Bridged metallocenes catalyst for polymerization of olefins

ABSTRACT

Bridged metallocenes of Group IVb metals provide improved results when the bridge comprises a neutral electron-donor substituent of general formula 
     
         R&#39;&#34;Z R&#34;&#34;.sub.j 
    
     wherein 
     R&#39;&#34; is a rigid unsaturated hydrocarbon radical between Z and the bridge, such that Z is separated from the bridge by 2 to 5 carbon atoms 
     Z is nitrogen, phosphorus, oxygen or sulphur, 
     R&#34;&#34; is H or an alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl having a maximum of 15 carbon atoms, each R&#34;&#34; being the same or different, 
     j is 1 when Z=O or S and 2 when Z=N or P.

This application is a division of application, Application Ser. No.08/562,319 filed on Nov. 22, 1995 and now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to bridged metallocene compounds. Moreparticularly, it relates to bridged dicyclopentadienide derivatives ofGroup IVb metals. It also relates to the use thereof in catalyst systemsfor the polymerization of olefins.

2. Description of the Prior Art

Metallocene catalysts suffer from a disadvantage in that the polyolefinproduct has small particle size and low bulk density. There is thereforea need in the art for a catalyst system that would retain advantages formetallocene catalyst systems but eliminate the above-mentioneddisadvantage thereof.

Morphology improvements have generally been obtained by immobilizing themetallocene on an inorganic carrier or on an organic functionally activecarrier, for the purpose of heterogenization.

U.S. Pat. Nos. 5,145,819 and 5,243,001 and EP-A-582195 disclose bridgedmetallocenes wherein alkoxy substituents can be attached directly to thebridge.

EP-A-608054 generically discloses bridged metallocenes wherein thebridge may have as substituent a 1-20 C hydrocarbyl containing oxygen,phosphorus, nitrogen or sulphur.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide bridgedmetallocenes for use in catalyst systems which produce polyolefins withlittle or no small particle size.

Another object of this invention is to provide bridged metallocenes foruse in catalyst systems which produce polyolefins with high bulkdensity.

A further object is to provide bridged metallocenes which when used donot give reactor fouling or crust formation.

These and other objects are accomplished by the use of a neutralelectron-donor substituent on the bridge of bridged metallocenes asdescribed and claimed below.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings in which like numerals in different figuresrepresent the same structures or elements wherein:

FIGS. 1 and 2 are representations of the structure of(Cp)(Flu)C(CH₃)(p-PhOCH3)ZrCl₂.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides for the use of a neutral electron-donorsubstituent on the bridge of bridged metallocenes, said substituenthaving the formula

    R'"Z R"".sub.j

wherein

R'" is a rigid unsaturated hydrocarbon radical between Z and the bridge,such that Z is separated from the bridge by 2 to 5 carbon atoms,

Z is nitrogen, phosphorus, oxygen or sulphur,

R"" is H or an alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl having amaximum of 15 carbon atoms, each R"" being the same or different,

j is 1 when Z=O or S and 2 when Z=N or P.

More specifically, the preferred bridged metallocenes (i.e. bridgeddicyclopentadienide derivatives) of Group IVb metals are of the generalformula

    (CpR.sub.4)--C.sub.m H.sub.2m --YR'.sub.k R".sub.2-k --C.sub.n H.sub.2n --(CpR.sub.4)MQ.sub.2

wherein

M is a Group IVb metal (Ti, Zr, Hf),

Q is a hydrocarbyl radical having from 1 to 20 carbon atoms or ahalogen, each Q being the same or different,

Cp is a cyclopentadienyl ring,

R is a substituent on a cyclopentadienyl ring and can be H or ahydrocarbon radical having 1 to 9 carbon atoms, each R being the same ordifferent,

each (CpR₄) being the same or different,

m is 0, 1, 2 or 3,

n is 0, 1, 2, or 3,

m+n is 0, 1, 2 or 3,

k is 1 or 2

Y is C or Si

R' is a neutral electron-donor substituent of general formula

    R'"Z R"".sub.j

wherein

R'" is a rigid unsaturated hydrocarbon radical between Z and the bridge,such that Z is separated from the bridge by 2 to 5 carbon atoms

Z is nitrogen, phosphorus, oxygen or sulphur,

R"" is H or an alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl having amaximum of 15 carbon atoms, each R"" being the same or different,

j is 1 when Z=O or S and 2 when Z=N or P,

R" is as indicated for R"".

The preferred Group IVb metals are hafnium and zirconium, the mostpreferred being zirconium. The preferred Q is a hydrocarbyl radicalhaving 1 to 3 carbon atoms or a halogen, the most preferred beingchlorine or bromine. As to the CpR₄ components, they are selectedaccording to the principles known in the art, in order to obtain thedesired properties of the polymer.

Whilst not wishing to be bound by a theory, it is believed that thisinvention lies in the improvement provided by the R' substituent(s) onthe bridge as compared to the same bridged metallocene without R'substituent(s).

As to the bridge, m and n are preferably O, and Y is preferably C.

As to the R' bridge substituent(s), k is preferably 1, R'" preferablyforms aromatic ring and is most preferably p-phenylidene, Z ispreferably O or N, and R"" is preferably H or methyl or ethyl (mostpreferably methyl or ethyl).

As to the R" bridge substituent, it is preferably H or alkyl up to 4carbon atoms or aryl, most preferably H or methyl.

The metallocene can be prepared by any suitable method e.g. as describedin U.S. Pat. No. 5,117,020, hereby incorporated by reference. Aparticularly suitable method for preparing fulvenes is described in theExamples, based on the methods by Stone and Little, J. Org. Chem., vol.49, p. 1849 (1984), and Kresze and Goetz Chem. Ber., vol. 90, p. 2161,(1957), both hereby incorporated by reference.

The present invention further provides a catalyst system essentiallyconsisting of one or more of the bridged metallocenes of the inventiontogether with one or more co-catalysts. The preferred co-catalysts arethose of the alumoxane type, preferably methylalumoxane, which are wellknown in the art and need not be described here. The bridgedmetallocenes can be supported, but are preferably unsupported for thepurpose of this invention; suitable supports and techniques forsupporting metallocenes are also well known in the art and need not bedescribed here; the preferred co-catalysts for supported bridgedmetallocenes are of the alkylaluminum type, preferably trialkylaluminum,which are well known in the art and need not be described here.

The polymerization and, where applicable, pre-polymerization conditionsare well known in the art and need not be described here. The catalystsystems of the invention can be used to polymerize olefins, particularlyethylene, propylene or a mixture thereof, most particularly propylene.

The invention having been generally described, the following examplesare given as particular embodiments of the invention and to demonstratethe practice and advantages thereof. It is understood that the examplesare given by way of illustration and are not intended to limit thespecification or the claims to follow in any manner.

EXAMPLE 1 CATALYST BASED ON (Cp)(Flu)C(CH₃)(p-PhOCH₃)ZrCl₂

a. Preparation of the Fulvene

To a solution of freshly distilled cyclopentadiene (0.625 mol) andp-methoxyacetophenone (0.25 mol) in reagent grade methanol (360 ml) wasadded pyrrolidine (0.375 mol, freshly distilled under N₂).

The mixture was stirred under nitrogen at room temperature for 20 hours.

Acetic acid (23 ml) was then added to the solution. The reaction mixturewas diluted with ether and water (100 ml each). The aqueous portion waswashed with ether (2×250 ml) and the combined organics were washed withwater and brine (50 ml each), then dried over MgSO₄ and concentrated invacuo.

Purification by recrystallization from methanol affords 30 g of6-(4-methoxy-phenyl) 6-methyl-fulvene.

Yield: 61%. Melting point (M.P.): 66-67° C.

b. Preparation of the Ligand.

41.5 grams (0.25 mol) of fluorene were dissolved in 350 ml oftetrahydrofuran (THF) in a 500 ml round bottom flask equipped with aside arm and dropping funnel with pressure equalizer.

0.25 mol of methyllithium (CH₃ Li) were added dropwise as a 1.6 Msolution in ether. Stirring of the solution was continued for threehours.

After gas evolution had ceased, 100 ml of THF containing 0.25 mol of6-(4-methoxy-phenyl) 6-methyl-fulvene were added dropwise to thesolution. Stirring of the solution was continued overnight.

The resulting solution was then washed with 200 ml of a saturatedammonium chloride aqueous solution, then with water.

After evaporation of the solvents, a powder was recovered on the surfaceof the water. Recrystallization by dissolving the powder in 500 mlchloroform and addition of excess ethanol at 2° C. yielded a powder.

Yield: 60%. M.P.: 189-190° C.

c. Preparation of the Bridged Metallocene

Reaction of the Ligand with Alkyllithium

10 g (0.0368 mol) of the ligand were dissolved in 200 ml THF in a 500 mlround bottom flask equipped with a side dropping funnel.

0.0736 mol of methyllithium were added dropwise as a 1.6 M solution inether. Stirring of the solution was continued for three hours.

After gas evolution had ceased, the solvents were evaporated at 40° C.leaving a finely powdered product after about 2 hours.

Reaction of the Metal Salt with the Lithiated Liqand

0.0368 mol of the ligand dilithium derivative was dissolved in 175 ml ofcold methylene chloride at -78° C.

A slurry of 0.0368 mol of ZrCl₄ in 175 ml of cold methylene chloride waspoured in the flask containing the lithiated ligand solution. Themixture was stirred during two hours at -78° C., allowed to warm slowlyto room temperature (23° C.) and stirred for an additional 12 hours.

Insoluble white LiCl was filtered off before crystallizing a powder bycooling the red solution to -20° C. for 12 hours.

After decantation, the crystalline powder was washed several timesmethylene chloride at -20° C. and isolated by removing the solvent undervacuum.

Yield: 76%.

The structure of this metallocene compound is shown in FIGS. 1 and 2,which are two different perspectives of the molecular structure(excluding H atoms). Some important distances (expressed in 10⁻¹⁰ m)between atoms (named as in FIGS. 1 and 2, except for Z2 and Z31 whichare the centroids of the C5 rings containing respectively C2 and C31)and angles (expressed in degrees) are given hereafter:

    ______________________________________                                        Zr-C11      2.413       Zr-Z2   2.26                                          Zr-C12      2.425       Zr-Z31  2.17                                          Zr-C2       2.404       Zr-C31  2.447                                         Zr-C3       2.508       Zr-C32  2.448                                         Zr-C8       2.681       Zr-C33  2.532                                         Zr-C9       2.700       Zr-C34  2.527                                         Zr-C14      2.537       Zr-C35  2.438                                                    C11-Zr-C12                                                                             99.9                                                                 Z31-Zr-Z2                                                                             118.3                                                                 C31-C1-C2                                                                              99.1                                                                 C21-C1-C41                                                                            106.4                                                      ______________________________________                                    

d. Polymerization of Propylene

Four polymerizations were carried out in a two-liter Buchi-typeautoclave purged with nitrogen gas then kept at a temperature of 60° C.The catalyst and the co-catalyst (MAO, 10 ml of a 11 wt % solution intoluene) were precontacted during 3 minutes before being introduced inthe reactor with 1 l of propylene; the pressure in the reactor was of2.8 MPa. After 1 hour polymerization, the polymerization activity, thepolymer bulk density, the polymer melting point, the polymer molecularweight (weight-average) and the stereoregularity (as shown by the rrrrvalue) were determined; the values are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                               Cat     Activity B.D.   M.P.  M.sub.w                                                                             rrrr                               Example                                                                              (mg)    (kg/g · h)                                                                    (g/ml) (° C.)                                                                       kDa   (%)                                ______________________________________                                        1.1    2.3     4.5      0.40   122.4  76   78.4                               1.2    2.5     4.7      0.40   117.9  69   72.1                               1.3    8.0     10       0.39   123.6  75   75.8                               1.4    8.0     18       0.31   124.5  77   74.3                               2      2.5     28       0.4    128.7  69   76.5                               3      2.5     47       0.36   n.d.   73   77.8                               C1     2.0     190      0.06   137.1  93   84.2                               C2     2.0     127      0.07   134.8  109  82.9                               ______________________________________                                    

EXAMPLE 2 CATALYST BASED ON (Cp)(Flu)C(H)(p-Ph-SCH₃)ZrCl₂

a. Preparation of the Fulvene.

6-(4-methylthio-phenyl)-fulvene was prepared following the proceduredescribed in example 1a, except that the reaction time was 15'.

Yield: 96% ; M.P.: 105-6° C.

b. Preparation of the Ligand.

The ligand was prepared according to the procedure described in example1b.

Yield: 53%; M.P.: 186° C. (decomposition)

c. Preparation of the Catalyst.

The catalyst was prepared according to the procedure described inexample 1c.

Yield: 18%

d. Polymerization of Propylene

The procedure of example 1d was repeated, except as indicated in theTable; the pressure was of 2.6 MPa.

EXAMPLE 3 CATALYST BASED ON (Cp)(Flu)C(H)(--Ph--N(CH₃)₂)ZrCl₂

a. Preparation of the Fulvene.

6-(4-methylthio-phenyl)-fulvene was prepared following the proceduredescribed in example 1a, except that the reaction time was 1 hour.

Yield: 89% ; M.P.: 106-7° C.

b. Preparation of the Ligand.

The corresponding ligand was obtained according to the proceduredescribed in example 1b.

Yield: 77% ; M.P.: 218-9° C.

c. Preparation of the Catalyst.

The catalyst was prepared according to the procedure described inexample 1c.

Yield: 22%.

d. Polymerization of Propylene

In example 3, the procedure of example 1d was repeated, except asindicated in Table 1.

COMPARATIVE EXAMPLES Catalysts based on (Cp)(Flu)Rc

The catalyst systems were prepared and used as described in example1b/1c/1d. In Comparative Example C1, the Rc bridge was methyl isopropylmethylidene, in C2 methyl isobutyl methylidene.

In addition to the bulk density of the polymer being lower than whenusing the catalysts according to the invention, the particle size wassmaller, and the polymer contained a large amount of fines.

EXAMPLES 4 TO 6 SUPPORTED CATALYST

Pretreatment of the Support

gamma-Al₂ O₃ (10 g) was heat treated for 4 hours. It was then suspendedin toluene (Na-dried, 50 ml) and MAO (methylalumoxane, as 11 wt %solution in toluene) was added dropwise. The slurry was stirred for 30min. at room temperature.

At the end of this period it was filtered and the solid so obtained waswashed 2 times each with Na-dried toluene then with CaH₂ -dried pentaneand dried under vacuum.

Preparation of the Supported Catalyst.

Catalyst as described in example 3 was dissolved in toluene (Na-dried20-30 ml). Pretreated gamma-Al₂ O₃ was added and a slurry was obtained.It was stirred at room temperature for 30 minutes.

After decantation of the supernatant liquid, the solid was washed 3times each with toluene, then with pentane (CaH₂ -dried) and dried undervacuum.

The experimental conditions were as follows:

example 4:

heat treatment at 900° C.

0.5 g MAO/10 g alumina

example 5:

heat treatment at 300° C.

1.4 g MAO/10 g alumina

example 6:

heat treatment at 300° C.

2.5 g MAO/10 g alumina

Polymerization of propylene was carried out as described in example 1d,except as indicated in Table 2.

The results are indicated in Table 2. They demonstrate that the processof the invention is more efficient to improve morphology than depositionon a support.

                  TABLE 2                                                         ______________________________________                                               Catalyst/                                                                              Supported MAO           Bulk                                         support  catalyst  (11 wt %)                                                                            Activity*                                                                            density                               Example                                                                              (g/g)    (g)       (ml)   (kg/g · h)                                                                  (g/ml)                                ______________________________________                                        4.1    0.02     1         3      1.8    0.30                                  4.2    0.01     1         3      4.0    0.30                                  5.1    0.02     1         3      1.4    0.35                                  5.2    0.01     1         3      1.2    0.35                                  5.3    0.01     1         10     1.1    0.35                                  6.1    0.02     1         3      1.3    0.30                                  6.2    0.02     1         10     3.3    0.30                                  ______________________________________                                         *calculated on the weight of metallocene used.                           

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letter of Patent ofthe United States of America is:
 1. Catalyst systems for thepolymerization of olefins, essentially consisting of one or more bridgedmetallocenes having the formula

    (CpR.sub.4)--C.sub.m H.sub.2m --YR'.sub.k R".sub.2-k --C.sub.n H.sub.2n --(CpR.sub.4)MQ.sub.2

wherein C_(m) H_(2m) --YR'_(k) R"_(2-k) --C_(n) H_(2n) -- is the bridgewith substituents, M is a Group IVb metal, Q is a hydrocarbyl radicalhaving from 1 to 20 carbon atoms or a halogen, each Q being the same ordifferent, Cp is a cyclopentadienyl ring, R is a substituent on acyclopentadienyl ring and can be H or a hydrocarbon radical having 1 to9 carbon atoms, each R being the same or different, each (CpR₄) beingthe same or different, m is 0, 1, 2 or 3, n is 0, 1, 2, or 3, m+n is 0,1, 2 or 3, k is 1 or 2 Y is C or Si R' is a neutral electron-donorsubstituent of general formula

    R'"Z R"".sub.j

wherein R'" is a rigid unsaturated hydrocarbon radical between Z and thebridge such that Z is separated from the bridge by 2 to 5 carbon atoms Zis nitrogen, phosphorus, oxygen or sulphur, R"" is H or an alkyl,cycloalkyl, aryl, alkylaryl or arylalkyl having a maximum of 15 carbonatoms, each R"" being the same or different, j is 1 when Z=O or S and 2when Z=N or P, R" is as indicated for R"" and one or more alumoxaneco-catalysts.
 2. Catalysts system according to claim 1, wherein in theco-catalyst is methylalumoxane.
 3. Catalyst systems for thepolymerization of olefins, essentially consisting of one or more bridgedmetallocenes supported on a support, said metallocenes having theformula

    (CpR.sub.4)--C.sub.m H.sub.2m --YR'.sub.k R".sub.2-k --C.sub.n H.sub.2n --(CpR.sub.4)MQ.sub.2

wherein C_(m) H_(2m) --YR'_(k) R"_(2-k) --C_(n) H_(2n) -- is the bridgewith substituents M is a Group IVb metal, Q is a hydrocarbyl radicalhaving from 1 to 20 carbon atoms or a halogen, each Q being the same ordifferent, Cp is a cyclopentadienyl ring, R is a substituent on acyclopentadienyl ring and can be H or a hydrocarbon radical having 1 to9 carbon atoms, each R being the same or different, each (CpR₄) beingthe same or different, m is 0, 1, 2 or 3, n is 0, 1, 2, or 3, m+n is 0,1, 2 or 3, k is 1 or 2 Y is C or Si R' is a neutral electron-donorsubstituent of general formula

    R'"Z R"".sub.j

wherein R'" is a rigid unsaturated hydrocarbon radical between Z and thebridge such that Z is separated from the bridge by 2 to 5 carbon atoms Zis nitrogen, phosphorus, oxygen or sulphur, R"" is H or an alkyl,cycloalkyl, aryl, alkylaryl or arylalkyl having a maximum of 15 carbonatoms, each R"" being the same or different, j is 1 when Z=O or S and 2when Z=N or P, R" is as indicated for R"" and one or more alkylaluminumco-catalysts.
 4. Catalysts systems according to claim 3, wherein theco-catalyst is a trialkyl aluminum.